1. Field of the Invention
The present invention relates to an obstacle avoidance system with an ultrasonic sensor. More particularly, the present invention relates to an obstacle avoidance system with an ultrasonic sensor which replaces distance data of a frame determined as noise with an average from distance data of frames prior to and after the noise frame, calculates an amount of orientation change of another frame using an orientation tracker, and regards distance data of another frame as noise if the calculated amount of orientation change is greater than a threshold, thereby resolving the problems caused by the ultrasonic sensor.
2. Description of the Related Art
In general, blind or visually impaired people walk on streets using a white cane or a guide dog. When using a white cane, the blind or visually impaired pedestrian can sense only a small area and is forced to slow his or her pace. On the other hand, while a guide dog may allow the blind or visually impaired pedestrian to walk safely, he or she must pay a training fee for the guide dog. Also blind or visually impaired people cannot enter many places due to animals not being allowed. In order to resolve these problems, various obstacle avoidance systems and methods have been developed.
For example, there are an electronic travel aid (ETA) and a robotic travel aid (RTA) that assist blind or visually impaired people in traveling.
The RTA is an apparatus configured in such a way that a robot senses obstacles and guides the blind or visually impaired person. The RTA is advantageous in that it can employ a high performance computer because it depends on the performance and mobility of the robot but is not restricted by its weight. However, the RTA has a drawback in that it can only move horizontally. So, compared to the ETA, the mobility of the RTA is relatively restricted.
The ETA is an apparatus that uses an electronic controller to assist a blind or visually impaired pedestrian in traveling. Such an ETA is implemented by a wearable computing device. The device is operated in such a way that a CCD camera shoots the front image and a travelable path is calculated using an image processing method. However, the image processing method is disadvantageous in that it requires a large amount of calculation to obtain the desired information and thus takes a long time. The wearable computing device may be implemented to include an ultrasonic sensor that senses obstacles. The ultrasonic sensor is relatively lower in price and less harmful than a laser range scanner, but has drawbacks in that it causes serious noise due to signal scattering or signals attenuation. In particular, these conventional obstacle avoidance methods, which use an ultrasonic sensor, have disadvantages in that, since they do not consider vibration from a pedestrian's travel, the avoidance orientation frequently changes.